Effects of air-abrasion pressure on the resin bond strength to zirconia: a combined cyclic loading and thermocycling aging study

Abstract

Objectives: To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide (Al₂O₃) particles at different pressures.

Materials and methods: Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and χ² tests (α = 0.05).

Results: The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure.

Conclusions: CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.

Keywords: Air-abrasion; Bond strength; Fatigue; Panavia F 2.0; Resin cement; Thermocycling.

Figure 1

Zirconia specimen with resin cement adhered. (A) Zirconia specimen embedded in acrylic resin; (B) Placement of the specimen on the Ultradent jig coupled with the semicircular plastic mold; (C) Zirconia specimen after resin cement button fabrication.

Figure 2

Fatigue cyclic loading and shear bond strength test apparatus. Fatigue cyclic loading was applied in a shear direction parallel to the adhesive interface using an Ultradent loading jig with a semicircular loading surface (2.4 mm in diameter) in close proximity to the zirconia-resin button interface and subjected to 10 N load for 10,000 cycles with a frequency of 1.0 Hz. (A) Frontal-view of the testing apparatus; (B) A close up for the testing setup.

Figure 3

Mean surface roughness and standard deviations of different groups after air-abrasion. Control group represents the zirconia surface before air-abrasion treatment. Ra, average surface roughness; 1b, 1 bar; 2b, 2 bar; 2.8b, 2.8 bar. ^a,bDifferent letters represent significant differences among the air-abrasion pressures tested.

Figure 4

Scanning electron microscopic images (× 2,000) of zirconia surface for control and after different air-abrasion pressures. (A) Control group (no air-abrasion); (B) 1 bar; (C) 2 bar; (D) 2.8 bar.

Figure 5

Scanning electron microscopic images of zirconia surface denoting mixed mode of failure after debonding at magnification (A) × 30; (B) × 300.